Editor’s Note (January 10, 2023): This article states that as the town of Montecito, California was evacuated on Monday, torrential rains from atmospheric river storms could trigger deadly landslides like the Thomas Fire scars. It has been republished due to its nature. What happened exactly five years ago.
At 3:30 am on January 9, 2018, half an inch of rain fell on the charred slopes of the Santa Ynez Mountains on the Southern California coast. Flames from the Thomas Fire, then the largest wildfire in state history, raged the previous month, scorching soil and vegetation and unable to absorb the waters of the onslaught. Unstable ground gave way with devastating landslides. Rocks crashed into homes in the town of Montecito, California, burying a highway under several feet of mud. The disaster killed 23 people and caused him an estimated $200 million in damage.
Climate scientist Samantha Stevenson recently moved to the state to start a new job at the University of California, Santa Barbara. “As someone who had just arrived in California, she was so devastated,” she says. “She got something stuck in her head.”
Years later, when Stevenson and Daniel Thoma, then a postdoctoral fellow at the University of California, Santa Barbara, were scouring for research ideas, memories of landslides led to the idea that extreme rains could lead to massive wildfires. is high. change.Their work published on Friday scientific progress, By the end of the century, we found that most wildfires across much of the West would be followed by some extreme rain within five years. This carries with it a great risk of landslides and flash floods.
And these risks are not confined to the decades ahead. Studies have shown that the likelihood of this kind of compound event occurring is already rising across the West. ‘ says Stevenson.
Climate scientists combine historical data with computer models to look for trends in how the severity and frequency of extreme weather events have already changed and will continue to do so. These efforts have already revealed that wildfires in the western United States are likely to become more intense and burn larger areas, and that heavy rains are likely to become more frequent and intense.
But such events “don’t just happen in isolation,” Stevenson says. Together, they can cause dramatically more damage to communities than any one event alone, like the heavy rains that caused the 2018 Thomas Fire burn scars.
However, by their very nature, such extreme compound events are relatively rare. This means that there is often not enough historical data to identify trends in how these events will change as global temperatures rise. A lot of people ask us, ‘Are these going to get worse?'” says Touma. Prior to her and Stevenson’s new study, “no full answer could be given regarding these complex events.”
To investigate this question, Touma, Stevenson, and their co-authors set out from a number of run-of-the-mill climate models that provide enough scenarios for scientists to identify trends in this type of extreme weather. We turned to newly available data. “We have more data than we used to,” Stevenson says. “So we can start to say quantitative things about rare events of this kind.”
Researchers found that by 2100, more than 90% of wildfires in California, Colorado and the Pacific Northwest will be followed by at least three extreme rainfall events within five years. . The number of fires following rainfall within just one year (higher risk of landslides) is set to double in California by the end of the century. That number is projected to rise 700% in the Pacific Northwest, he says, as expected extreme rainfall increases significantly. “We expected to see a signal,” Stevenson said, but the increase in magnitude was “very severe.” The overall results were “not surprising,” she adds. “But it was pretty chill.”
And such concerns will become important long before the end of this century. Even in 2050, fires will be followed by heavy rains that are much more likely, says Touma. The findings provide insight into how risks change if greenhouse gas emissions are curbed and warming is held to lower levels. (The model the team used assumes a worst-case emissions scenario of relatively high levels of warming by 2100.)
“These types of studies help draw attention to these emerging and complex climate risks that we are increasingly seeing,” said Kai Kornhuber, a climate scientist at Columbia University. “It’s important to raise awareness,” he said. “I’m sure there will be more studies like that.”
Stevenson and Thoma say they hope their research will help emergency management preparedness and community adaptation. In response to the Marshall fires that destroyed more than 1,000 homes in his Boulder County, Colorado, last December, officials are providing resources to residents to clear the area of debris in preparation for the spring rains, he said. says Touma. National Atmospheric Research Center in Boulder, Colorado. The day after the Marshall Fires broke out, a massive snowstorm helped put the flames out. But in a warmer future, that snow could turn into rain, exacerbating devastation. “We’re not going to prevent” such an event, Stevenson says, so “we need to be prepared.”
